Characterization of reduced-pressure chemical vapor deposition polycrystalline silicon germanium deposited at temperatures =550 deg C

摘要

This paper investigates the possibility of reducing the deposition temperature of polycrystalline silicon germanium to a level compatible with complementary metal-oxide semiconductor (CMOS) post processing. To achieve this goal, the exact wafer temperature during deposition was experimentally determined and it was found to be 30 deg C lower than the reactor setting temperature. The deposition temperature was reduced from 625 to 500 deg C. The impact of varying the deposition pressure from 10 to 760 torr and the germanium content from 15 percent to 100 percent was investigated. X-ray diffraction spectroscopy and transmission electron microscopy showed that the Si_xGe_(1-x) films deposited at an actual wafer temperature of 520 deg C are polycrystalline for germanium contents as low as 15 percent. Also, it was shown that the deposition conditions can be adjusted to yield a low tensile stress at an actual wafer temperature of 520 deg C, which is suitable for integrating surface micromachined micro-electromechanical systems on top of standard CMOS wafers with Al interconnects.